This invention relates to a light supply device for an endoscope, and more particularly to a light supply device which supplies an endoscope with a light of desired intensity and has a prescribed insulation withstand voltage property.
An endoscope light supply device is generally included in medical electric equipment. Therefore, an endoscope light supply device should meet an item included in the safety regulations of various countries as well as those of international scope (e.g. UL, IEC, etc.), namely, a specification related to the insulation withstand voltage. This insulation withstand voltage specification prescribes that the abovementioned endoscope light supply device needs to be provided with an insulation withstand voltage property of at least 5,000 volts.
The conventional endoscope light supply device comprises a patient circuit connected to an endoscope to be introduced into a patient's coeliac cavity and a primary circuit directly connected to a commercial A.C. power source. A flash tube for emitting a light to photograph an affected portion of the patient's coeliac cavity is connected to the primary circuit, and actuated in response to a signal transmitted from the patient circuit. Further, to assure the aforesaid insulation withstand voltage property, the patient circuit and primary circuit are optically connected together and yet electrically isolated by means of an optoisolator.
With the prior art endoscope light supply device, however, the optoisolator for connecting the patient circuit to the primary circuit has a low withstand voltage. Where, therefore, a high voltage of, for example, 5,000 volts is impressed between the patient circuit and primary circuit, the optoisolation is very likely to be destroyed. Viewed this way, the conventional endoscope light supply device has the drawbacks that it does not fully meet the insulation withstand voltage specification included in the international safety regulations, and can not be regarded as completely safe for the patient, for example.
A pulse transformer acting as magnetic coupling means which might replace the optoisolator still has the drawbacks that the pulse transformer having a large size unavoidably renders an endoscope light supply device bulky; leads to an increase in the production cost of the above-mentioned device; and is unadapted to be used with an endoscope light supply device demanded to quickly process a signal, because the pulse transformer transmits a signal at a slower rate than the optoisolator.
It is accordingly the object of this invention to provide a light supply device for an endoscope which is quickly actuated and which is extremely safe for the human body.